Skin graft devices and methods

ABSTRACT

Devices and methods for obtaining a plurality of skin tissue particles for use in skin grafting.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/451,174, filed Apr. 19, 2012, which claims the benefit under 35 USC119(e), of the filing of U.S. Provisional Patent Application No.61/477,485, entitled “Skin Graft Devices and Methods,” filed Apr. 20,2011, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates generally to skin grafting and relateddevices and methods. The present invention provides a systematicapproach to the process of skin grafting, i.e., harvesting,post-excision processing and application of donor skin and treatment ofthe graft recipient site.

2. Background Information

Advances in medical technology have provided many patients with benefitsinconceivable a century ago. In particular, skin grafting has enableddoctors to heal wounds with the patient's own skin from a harvest siteon the patient. The skin grafting techniques have many wonderfulbenefits, but are still replete with a number of problems.

The process of split-thickness skin grafting can be envisaged as aseries of steps; (1) harvesting the split-thickness-skin graft (“STSG”)at a donor site; (2) processing of excised STSG; (3) application of theprocessed skin to the wound site; and (4) pre- and/or post-grafttreatment to accelerate healing of the wound site. Each of these stepsinterposes various challenges and obstacles, e.g., technical,therapeutic and financial, in executing a successful graft.

In regard to the first step, harvesting a STSG at a donor site hastraditionally been accomplished using powered, hand-held dermatomes.These devices are expensive and the operation is known to be highlydependent on user skill and training, and requires involved proceduresto accurately obtain a successful harvest. These devices must beoperated at a precise constant angle relative to the skin, with theexact amount of pressure to insure a uniform harvest. Slight variationsin operative use of these dermatomes result in excised skin ofvariable-thickness, which sometimes must be discarded altogether. As aresult, these devices are primarily wielded only by experienced plasticsurgeons. Use of these dermatomes are generally confided to theoperating room setting, increasing the cost of the procedure, especiallygiven the average fee for operating room use.

There is a current need for harvesting procedures that require a lowerdegree of operator skill and are capable of being performed outside ofan operating room, thus decreasing the costs of the procedure.

In regard to the second step of processing excised skin, it is highlydesirable to maximize the coverage of the donor skin at the wound sitefor any given area of a potential donor site. Apart from minimizingtrauma incurred at the donor site, a major factor limiting survivalfollowing extensive injury is insufficient availability of donor sitesto provide enough skin for the required grafting procedures. Oneprocedure is to mesh the skin graft i.e., creating slits in the exciseddonor skin to allow for the skin to be stretched. A graft-meshingmachine is commonly used in hospital-based surgical practices, andgenerally allow for an expansion ratio of 3:1 to 9:1. The excisedharvested skin is placed on a specific template, depending on theexpansion ratio desired, and the template and graft are pressed throughthe mesher. While greater ratios than 9:1 may be possible using meshingtechniques, there is a concomitant significant delay inepithelialization with using such ratios. When healed, a meshed graftedsite characteristically has a permanent “crocodile skin” or “weaved”appearance.

Micro grafting techniques, in which the donor tissue is actually mincedin order to achieve a greater than 10:1 expansion ratio, are known inthe art. Such techniques allow for a greater coverage area from a smalldonor site than meshing techniques. Traditional micrograft techniques,dating back to 1963, utilized minced skin that is between ⅛th inch(approximately 3 mm, or 3000 μm) and 1/16th inch (approximately 1.5 mm,or 1500 μm) in size. However, disadvantages of using pieces larger than1500 μm have been noted. For example, in skin pieces of this size cellsremote from a cut edge have a limited availability to migrate andproliferate and thereby contribute to forming new skin. In addition, thetechniques employed have required each piece to be oriented epidermisupwards, making the procedure tedious and impractical. Further, theappearance of the new skin that is produced using particles of this sizeis poor, often having a cobblestone appearance.

There is currently a need for a procedure capable of producingmicrograft particles in a size less than 1500 μm in a rapid andefficient manner, with a minimum of handling procedures, while resultingin skin pieces that are viable and capable of “taking” when applied to awound site. Such technique would significantly aid in the ease and speedof operations utilizing micrografts.

The third step of the graft procedure, application of processed excisedskin to the wound site, it is particularly relevant to the applicationof micrograft particles to a wound site. Current methods of distributingmicrografts, such as mechanical spreading results in clumps oraggregates of skin particles, frustrating an even distribution. Inaddition, in larger aggregates, some micrograft particles will not be indirect contact with the wound bed. Such particles cannot readilyintegrate with the wound bed and also will have a reduced potential fornourishment from the wound fluid exudates and consequently have adecreased potential to remain viable. Thus, the aggregation ofmicrografts reduces the efficiency of epithelialization and maysignificantly increase the time required to close a wound.

There is a current need for devices and methods to effect an evendistribution of micrcograft particles on a wound surface, therebypromoting the efficiency of epithelialization.

The fourth step of the graft procedure relates to pre- and/or post-grafttreatment to accelerate healing of the wound site. As is known in theart, closure of surface wounds involves the inward migration ofepithelial, dermal and subcutaneous tissue adjacent to the wound. Thismigration is ordinarily assisted through the inflammatory process,whereby blood flow is increased and various functional cell types areactivated. Through the inflammatory process, blood flow through damagedor broken vessels is stopped by capillary level occlusion; thereafter,cleanup and rebuilding operations may begin.

SUMMARY

Certain embodiments of the present disclosure comprise devices andmethods relating generally to skin grafting. Particular embodimentsprovide a systematic approach to the process of skin grafting, i.e.,harvesting, post-excision processing and application of donor skin andtreatment of the graft recipient site.

Certain embodiments of the present disclosure comprise a device forobtaining a plurality of skin tissue particles for use in skin grafting.In particular embodiments, the device includes a dressing comprising afirst surface configured to retain a plurality of skin tissue particles;a housing configured to receive the dressing, wherein the housingcomprises a first aperture configured to be coupled to a vacuum source;and a plurality of hollow needles proximal to the first surface of thedressing. In certain embodiments, the first surface comprises a gel. Inspecific embodiments, the gel is a polyurethane film, an extra-cellularmatrix (e.g. collagen), or a silicone based polymer.

In particular embodiments, the plurality of hollow needles are tapered.In specific embodiments, the plurality of hollow needles are taperedsuch that each of the plurality of needles comprises a larger endproximal to the first surface of the dressing. In certain embodiments,the housing comprises a seal configured to extend around the pluralityof hollow needles. In particular embodiments, during use, the pluralityof hollow needles are placed proximal to a donor site contained withinthe seal.

In specific embodiments, the dressing is located between the pluralityof hollow needles and the first aperture. In particular embodiments, thedressing is removable from the housing, and in certain embodiments, thehousing comprises a first aperture configured to be coupled to abellows.

Exemplary embodiments also comprise a method of obtaining a plurality ofskin tissue particles for use in skin grafting, the method comprising:placing a first device according to claim 1 onto a first donor site;applying negative pressure to the first device; removing a firstplurality of skin tissue particles from the first donor site; removing afirst dressing from the housing of the first device, wherein the firstplurality of skin tissue particles are retained on the first surface ofthe dressing; and placing the first dressing on a graft site, where thefirst plurality of skin tissue particles are proximal to the graft site.

Particular embodiments may also comprise covering the dressing and thegraft site with a drape; and applying negative pressure to a regionunder the drape. Certain embodiments may further comprise: placing asecond device onto the donor site and applying negative pressure to thesecond device; removing a second plurality of skin tissue particles fromthe donor site; removing the second dressing from the housing of thesecond device, wherein the second plurality of skin tissue particles areretained on the first surface of the second dressing; and placing thesecond dressing on the graft site, wherein the second plurality of skintissue particles are proximal to the graft site.

Certain embodiments may also comprise a device for obtaining a pluralityof skin tissue particles for use in skin grafting, the devicecomprising: a processor configured to process skin tissue into aplurality of skin tissue particles; and a container configured to retainthe plurality of skin tissue particles, wherein the processor comprisesa first cutting surface configured to penetrate skin tissue at a donorsite and a second cutting surface that rotates.

In particular embodiments, the first surface comprises a punchconfigured to penetrate skin tissue and the second cutting surface isconfigured to sever skin tissue from the donor site. In certainembodiments, the second cutting surface rotates in a plane generallyparallel to the skin tissue of the donor site. In specific embodiments,the second cutting surface rotates in a plane generally perpendicular tothe skin tissue. In particular embodiments, the processor is manuallyoperated. In certain embodiments, the processor is electrically powered.In specific embodiments, the device is configured such that the devicecan be separated from the processor.

The following drawings illustrate by way of example and not limitation.For the sake of brevity and clarity, every feature of a given structureis not always labeled in every figure in which that structure appears.Identical reference numbers do not necessarily indicate an identicalstructure. Rather, the same reference number may be used to indicate asimilar feature or a feature with similar functionality, as maynon-identical reference numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 illustrate perspective and section views of a first exemplaryembodiment.

FIGS. 6-14 illustrate section views of the embodiment of FIGS. 1-5during use.

FIGS. 15-18 illustrate perspective and orthographic views of a secondexemplary embodiment.

FIGS. 19-20 illustrate perspective and orthographic views of a thirdexemplary embodiment.

FIGS. 21-22 illustrate perspective and orthographic views of a fourthexemplary embodiment.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The term “coupled” is defined as connected, although not necessarilydirectly, and not necessarily mechanically; two items that are “coupled”may be integral with each other. The terms “a” and “an” are defined asone or more unless this disclosure explicitly requires otherwise. Theterms “substantially,” “approximately,” and “about” are defined aslargely but not necessarily wholly what is specified, as understood by aperson of ordinary skill in the art.

The terms “comprise” (and any form of comprise, such as “comprises” and“comprising”), “have” (and any form of have, such as “has” and“having”), “include” (and any form of include, such as “includes” and“including”) and “contain” (and any form of contain, such as “contains”and “containing”) are open-ended linking verbs. As a result, awound-treatment method that “comprises,” “has,” “includes” or “contains”one or more steps possesses those one or more steps, but is not limitedto possessing only those one or more steps. Likewise, a wound dressingthat “comprises,” “has,” “includes” or “contains” one or more elementspossesses those one or more elements, but is not limited to possessingonly those elements.

Further, a device or structure that is configured in a certain way isconfigured in at least that way, but it can also be configured in otherways than those specifically described.

Referring now to FIGS. 1-5, a device 100 for obtaining skin tissueparticles for use in skin grafting is shown. Device 100 comprises ahousing 110 that is configured to receive a dressing 120. In certainembodiments, housing 110 may comprise a first portion 111 and a secondportion 112 that may be coupled together or separated to allow thecontents within housing 110 to be removed. In the embodiment shown,device 100 also comprises a plurality of hollow needles 130, which areconfigured to penetrate tissue during use and remove skin particles froma harvest site. In the illustrated embodiment, device 100 furthercomprises a seal 150 configured to seal an area around the plurality ofneedles 130.

An overview of the operation of device 100 will be provided initially,followed by a more detailed description. During operation, device 100can be placed on a skin harvest site such that hollow needles 130 are incontact with the harvest site and seal 150 has sealed the area withinthe harvest site. A low pressure source 116 (e.g. a bellows device, avacuum pump or other suitable device) can be coupled to aperture 140 andoperated to provide a low pressure region within housing 110. In theembodiment shown, a switch 115 can control operation of low pressuresource 116.

The operation of low pressure source 116 can cause air to flow in thedirection of arrow 145 (see FIG. 3) and draw the harvest site towardneedles 130. Skin tissue from the harvest site can be drawn into needles130 and removed from the harvest site. In certain embodiments, device100 may be vibrated or laterally translated to assist in the removalskin tissue from the harvest site. In particular embodiments, hollowneedles 130 may be tapered as shown in the cross-section view of FIG. 5such that an end 131 proximal to dressing 120 is larger than an end 132distal from dressing 120.

When the skin tissue is removed from the harvest site, the tissueparticles contact dressing 120, which includes a surface 121 that isconfigured to retain the particles when dressing 120 is removed fromhousing 110. A perspective view of dressing 120 removed from housing 110is shown in FIG. 4. Dressing 120 can then be placed on a graft siteoriented such that surface 121 and the tissue particles are in contactwith the graft site. In certain embodiments, a negative pressure woundtherapy can then be applied to the graft site to assist in the graftingof the tissue particles to the graft site.

Referring now to FIGS. 6-13, a description of individual steps in anexemplary method of use will be provided. As shown in FIG. 6, device 100has been placed on a donor site 200 such that needles 130 are in contactwith the skin tissue at donor site 200 and seal 150 has sealed the areaof donor site around needles 130. Referring now to FIG. 7, a negativepressure source (in fluid communication with device 100 via aperture140) has been operated to provide a negative pressure to device 100.With negative pressure applied, tissue from donor site 200 is drawn intoneedles 130 to a controlled depth so that the tissue extends throughneedles 130 and to surface 121 of dressing 120. Device 100 can then bemanipulated (e.g. vibrated, laterally translated, or other suitableaction) to remove skin tissue particles 131 from donor site 200. Whendevice 100 is removed from donor site 200, skin tissue particles 131 areretained by surface 121 of dressing 120. In particular embodiments,surface 121 may comprise a gel configured to retain the skin tissueparticles by adhering the particles to the layer.

As shown in FIG. 8, device 100 has been removed from donor site 200 andsurface 121 has retained skin tissue particles 131 after removal fromdonor site 200. Referring now to FIG. 9, first portion 111 of device 100has been separated from second portion 112. This can allow dressing 120to be removed from housing 110 of device 100. As shown in thisembodiment, surface 121 continues to retain skin tissue particles 131with dressing 120 removed from housing 110.

Referring now to FIG. 10, dressing 120 is positioned proximal to a graftsite 300 so that skin tissue particles 131 are oriented proximal tograft site 300. As shown in FIG. 11, in certain embodiments, multipledressings 120 may be placed adjacent to each other in cases where graftsite 300 is larger than dressing 120. In specific embodiments, dressing120 may be configured so that multiple dressings can be placed adjacentto each other to substantially cover graft site 300. For example, incertain embodiments, dressing 120 and surface 121 may be triangular,square, rectangular, hexagonal or other suitable configurations (whenviewed from above looking down toward dressing 120 and graft site 300).

As shown in FIG. 12, dressing 120 is placed on graft site 300 so thatskin particles 131 are in contact with graft site 300. As illustrated inFIGS. 8-12, skin tissue particles 131 are retained by surface 121 fromthe time the particles are harvested from donor site 200 until they areplaced on graft site 300. The ability to retain skin tissue particles131 during the harvesting and grafting process provides many benefits,including the ability to provide a consistent and repeatable delivery ofthe particles to the graft site. This can increase the likelihood ofobtaining a successful graft and improve the uniformity of the graftappearance.

In certain embodiments, negative pressure wound therapy can also beapplied to graft site 300. As shown in FIG. 13, a drape 160 has beenapplied over dressing 120 and graft site 300. In the embodiment shown acoupling member 161 couples a conduit 162 to drape 160 and allows anegative pressure to be applied to the region under drape 160 (includinge.g., dressing 120 and graft site 300). As shown in FIG. 14, a largerdrape 160 may be used in cases where multiple dressings 120 are neededto cover graft site 300.

Referring now to FIG. 15-18, an exemplary embodiment comprises a unitarydermatome and mincer single use multi-bladed micro punch 400 with aplurality of nano-punches configured to incise the epidermis to therequired depth and dimension. The punch can be activated using the snapswitch situated on the side of the device. In this embodiment, adisposable tip also incorporates a specimen tray or container, where theprocessed skin particles are collected. Harvested material is releasedfrom the device by pressing the knob on the rear of the device. Thisembodiment provides a manual operation multi-specimen micro punch devicewith disposable tip and specimen tray/container. This device is able toharvest the skin particles (or islets) and process them to a ready touse state using simple operations. Additional details regarding thefeatures and operation of the embodiment of FIG. 15-18 can be found inthe figures and accompanying description in FIGS. 15-18.

Referring now to FIGS. 19-20, a unitary, battery powered, re-useabledermatome and mincer is shown. In this embodiment, the battery-powereddevice is placed on the donor site with moderate pressure and activatedusing the on/off trigger. During operation of this embodiment, the skintissue can be excised and transferred by vacuum to aremovable/disposable collection canister or container. In this exemplaryembodiment, the cutting head may also be a disposable component. Thecanister/container of this device provide easy access to fully processedskin particles. Additional details regarding the features and operationof the embodiment of FIG. 19-20 can be found in the figures andaccompanying description in FIGS. 19-20.

Referring now to FIGS. 21-22, a disposable, single-use skin mincer isillustrated. In this embodiment, the donor skin can be harvested using adermatome or Weck knife and then placed into the device. Exemplaryembodiments of this device comprise two contra-rotating blades which areoperated by rotating the handle, which grind the donor skin tissue intosmall particles. The finished skin particles can be ejected from thedevice once the required dimensions have been achieved. This embodimentprovides a unique method of processing the donor skin by using atwisting action to prepare the donor skin ready for grafting. Additionaldetails regarding the features and operation of the embodiment of FIG.21-22 can be found in the figures and accompanying description in FIGS.21-22.

The claims are not intended to include, and should not be interpreted toinclude, means-plus- or step-plus-function limitations, unless such alimitation is explicitly recited in a given claim using the phrase(s)“means for” or “step for,” respectively.

We claim:
 1. A device for obtaining a plurality of skin tissueparticles, the device comprising: a first portion having a conical endand a cylindrical end coupled to a base of the conical end and anaperture in an apex of the conical end, the first portion having a flowpath through the first portion from the aperture to the cylindrical end,the aperture configured to be coupled to a low pressure source; a secondportion having a first end configured to be coupled to the cylindricalend of the first portion to form a cavity, the second portion beingcylindrical and having a second end that is closed, the second portionbeing separable from the first portion; a plurality of needles coupledto the second end of the second portion, each of the plurality ofneedles being hollow and in fluid communication with the aperture whenthe second portion is coupled to the first portion; and a dressingconfigured to be disposed in the cavity and in fluid communication withthe aperture and the plurality of needles.
 2. The device of claim 1,wherein each of the plurality of needles is tapered, an end of eachneedle proximate to the second end of the second portion being largerthan a distal end.
 3. The device of claim 1, further comprising a sealcoupled to the second portion, the seal surrounding the plurality ofneedles.
 4. The device of claim 1, wherein the first portion furthercomprises a surface extending across the cylindrical end, the surfacehaving a plurality of apertures.
 5. The device of claim 4, wherein thecavity is formed between the surface extending across the cylindricalend of the first portion and the second end of the second portion. 6.The device of claim 1, wherein the cylindrical end of the first portionhas an outer diameter, the second portion has an outer diameter, and theouter diameter of the first portion is substantially the same as theouter diameter of the second portion.
 7. The device of claim 6, whereinthe second portion further comprises an annular tab having an outerdiameter less than the outer diameter of the second portion to form anannular shoulder, the annular shoulder configured to receive thecylindrical end of the first portion.